...Then a miracle occurs

"Irreducible Complexity" or gene duplication?

    Hemophilia A is an inherited X-linked recessive disease, characterized by improper clotting of the blood due to a deficiency in Coagulation Factor VIII.  Advocates of the theory of irreducible complexity have asserted that this cascade could not have evolved by natural selection, and therefore requires  an "Intelligent Designer" [a resurrection of the 18th-cent. "Argument from Design"]. For a rebuttal, see this excerpt form Darwin's God  by Kenneth R. Miller. The various coagulation factors turn out to be a gene family derived from a serine protease locus with the insertion of an EGF domain, which allows specific and localized blood clotting. The multiple factors amplify the small signal from the original cut as a cascade that promotes a major response, in the same manner as a photomultiplier tube.


Figure after © Sid Harris; all text material ©2009 by Steven M. Carr